1. Field of the Invention
The present invention relates to line lifts for such use as in servicing electrical and telephone lines and for maintaining right of ways for such lines. More particularly, the present invention relates to apparatus for extending the range of operation of such lifts.
2. Description of the Prior Art
A line lift is a device used for elevating an individual to a specific location above the ground surface, usually for maintenance purposes. For example, telephone repairmen who need to repair telephone wires strung from poles use line lifts mounted onto truck beds to reach those wires. Similarly, tree maintenance persons employ line lifts to elevate themselves to those areas of a tree requiring maintenance, such as trimming or dead branch removal.
A typical line lift incorporates a lower boom pivotally connected to a mast assembly at one end and an upper boom with a basket at a second end. A hydraulically operated expandable piston cylinder is connected to the lower boom. When the piston cylinder is expanded, it causes the lower boom to pivot upwardly in a direction away from the ground surface. The upper boom is extended by means of a hydraulically actuated pulley assembly attached to the lower boom, adjacent the upper boom. By extending the lower and upper booms, a person standing in the basket can be elevated to a specific location above the ground surface. One representative line lift of this construction is the Asplundh L-30 Series of line lifts manufactured by Asplundh Tree Expert Company.
Although such lifts operate extremely well, one problem some times associated with using such a line lift is that the boom has a limited range of rotation relative to the base of the mast assembly, usually less than 90 degrees. This limits the flexibility and degree of extension of the upper boom and basket. Thus, when an individual wishes to reach a specific location beyond the lift's normal range of extension, he must re-fold the booms, move the truck and then again unfold the booms, thereby expending additional time and effort in using the line lift.
Another problem associated with a line lifts' limited range of extension is that the vehicle on which the line lift is mounted must be parked on stable ground. Clearly the vehicle cannot be set up on soft ground or an excessive grade because this detracts from its stability and safety. However, often it is not possible to reach a specific location above the ground surface if the truck is parked on the spot where the ground is most stable and level. The operator is thus forced to forego maintainance or to secure his vehicle on less stable ground, thus exposing himself, the crew, and his vehicle to potentially hazardous consequences.
Finally, the situation may arise where the area requiring maintenance is inaccessible to a typical line lift having limited extension capabilities. If maintenance is to occur at all in these instances, a special aerial lift having elongated booms or less efficient maintenance means must be used.
Accordingly, it is a primary object of the present invention to provide a line lift having a greater range of flexibility and extension.
It is a further object of the present invention to provide such a lift with extended extension means which employs standard sized booms and adds minimal weight and complexity to existing lift equipment.